INFLUENCE OF CARDING LICKER-IN TYPE ON MELANGE YARN PRODUCTION

Prof. B. B. Jambagi* and R.Shiva Prakaash

D.K.T.E’S Textile and Engineering Institute, Ichalkaranji-416115 (India)

Email-shivaprakaash89@gmail.com

Abstract:

Due to their specific properties of aesthetics and comfort, melange cotton yarns are used

in the production of a variety of fabrics for shirting, home textiles products, underwear apparel

and sports. Melange yarns are spun from a number of fibres with different shades. The dyeing of

fibres are mainly two types i.e., flock dyed fibres and spun dyed fibres. During dyeing the fibre

get damaged in the sense change in fibre properties like strength, length. The higher degree of

damage of the dyed fibres mixed with white ones has a negative effect on the quality of the

melange yarn. The quality of the melange yarn depends considerably on the blending stage, as

well as the spinning systems1. In spinning process the carding has susceptible to more fibre

breakage and fibre damage. Our aim to reduce the fibre breakage in carding by using the pin-

type licker-in system and also study about the advantage and disadvantage of pin type licker-in

in cost wise also and quality wise also.

Keywords:

Melange yarn, polyester/cotton yarns, fibre breakage, pinned licker-in.

Introduction:

Melange yarns are spun from cotton or polyester fibers with different colors. Mixing

dyed and undyed fibers with varying degrees, it is a common method of producing of a variety of

fancy yarns. Mixing of fibers with different colors could be done either in the blow room at the

start of spinning preparation or by feeding different dyed fibers to the draw frames. Cotton

melange yarns are spun from a number of cotton fibers with different colors. Some Studies show

that scouring and dyeing process of cotton fibers lead to a greater entanglement and cohesion

among them, decreasing of fibers strength and removal of a part of the wax present on the

surface of cotton fibers. Further mechanical processes on these fibers lead to fiber damage and

decreasing of their length and strength parameters. These variations on fibers not only affect the

efficiency of spinning process, also mechanical and physical properties of the final yarn and

fabric1.

The main objects of carding are; The process of fibre opening to a state of individual

fibres, To remove neps, tiny lumps of fibres and fused fibre ends, To blend fibres and To deliver

a continuous sliver for further processing. After dyeing the fibre damage is more in the carding

process only because of metallic clothed rollers, speed of the different rollers and setting in the

carding. The change in physical properties is length, strength, fibre rupture and fibre damage2.

Melange yarn:

Melange yarn is the fiber dyed before spinning. The yarn is produced from color printed

tops or slivers. The color bands are short enough that each fiber has multiple colors. This results

in a heathered effect after spinning. Think of the individual hairs of a tabby cat. Individual hairs

are banded so they contain both black and grey on the same hair. When the hair is brushed off

the resulting effect is a heathered grey.

Fibre dyeing

Principle of dyeing

Adsorption of the dyestuff at the fibre surface

Diffusion of the dyestuff through the internal structure of the fibre

Fixation or ‘anchoring’ of the dye molecule at a suitable location or dye site3.

Type of fibre dyeing methods

Loose stock dyeing

Spun dyeing

Change in Fibre properties after dyeing

The change in fibre characteristics after dyeing is like

The fibre denier becomes coarser by 4-5%

The fibre tenacity decreases by 5-20%

The breaking elongation increases by 16-30%

The fibre friction increases4.

Dyeability of polyester fibre

Main reason for the poor dyeability of polyester fibres is a low diffusion of the dye

molecules into the fibre structure. Any change in fibre structure results in an altered dyeability of

the fibre. The effect of fibre structural changes, such as altered ratio of crystalline and

amorphous regions in drawing or changed size of pores in the fibre due to swelling, etc. on

dyeablility is determined by the so called accessibility of the fibres to dyes. There are three type

of polyester dyeing are carrier dyeing, HTHP dyeing and thermosol dyeing. The dyes used for

polyester is disperse dye5.

Loose stock or sliver dyeing

Dyeing of fibre prior to spinning is loose stock dyeing. Sliver dyeing is dyeing after the

sliver preparation to avoid shade variation due trash particles, to avoid entanglement.

The main advantages of fibre dyeing are more color ranges.

The disadvantages of loose stock dyeing are

problems of oligomers,

poor fastness properties,

shade variation,

change in the fibres properties after dying and

Environmental & Cost Benefits6.

Effect of oligomers during processing

Polyester fibres are currently dyed with disperse dyes at temperature around 125°C. All

polyester fibres contain, depending on their type, 1.5 to 2 percent of low molecular substances,

mostly cyclic oligomers which diffuse to the fibre surface at a High temperature and particularly

at high temperature settle together with dye particles, on the dyeing machine walls & on the fibre

surface. Oligomers deposited on the fibre surface are responsible for difficulties in subsequent

fibre processing. They increase dustiness & make the fibre surface rough. Mill trials showed that

addition of lubricants to the reducing clearing liquor results in part of the oligomers being bound

& the handle of the dyed polyester staple. Foreign polyester spinners recommend various types

of such lubricating agents, eg., the Bethamin 1199, Leomin HS 6 or Sromin SG 100. The percent

of oligomers content increases from 1.5% in grey to around 3% on dyeing in dark shades.

Oligomers tend to come out on to the surface on abrasion leads to lot of powder formation at the

trumpets. The card speeds have also to be dropped because of the oligomers. To reduce this

problem some of the mill doing reduction clearing at the rate of1-1.5g/liter and some mills are

doing double reduction clearing6.

Dope dyeing of polyester fibres

Spun-dyeing is achieved by adding the dyestuff, most often insoluble pigments, to the

initial raw material or directly to the polymer melt before spinning. Spun-dyeing of man-made

offers several economical and technical advantages; they particularly high output. The main

economical advantage over surface dyeing from solution dyeing is a 100% dye yield. Moreover,

there is complete saving of dye-house equipment and partial machinery savings in winding

rooms and finishing plants. Mechanical wear of the textile material is greatly reduced and

savings in transport and labor costs are also significant7.

Change in properties after dyeing: cotton

A literature review shows that cotton fibres suffer from a rather low decrease in strength

after being dyed, especially with reactive and indigo dyes. Dyeing cotton fibres leads to their

greater entanglement and cohesion. Moreover, due to the removal of a large portion of the wax

present on the surface of cotton fibres during the scouring and dyeing process, the average length

of cotton fibres decreases with a higher rate than that of white cotton fibres after going through

the blending, carding and drawing process. The fibre damage not only affects the efficiency of

the spinning process, but also the mechanical properties of the final yarn and fabric. We mainly

focus on fibre breakage during processing.

Clegg8 reported that the 5% portion of damaged fibres in a cotton bale increased to 54%

in the spun yarn. Rebenfeld9 studied the effect of several processing stages on the mechanical

properties of cotton fibre; he established that all the processing stages affect the mechanical

properties of cotton fibres, and their extent is process-dependent, as in bleaching, mercerizing

and resin finishing, which generally alter the fibre properties more than mechanical actions such

as carding, spinning and weaving.

Koo10 et al studied the strength, elongation, unevenness and spinnability of component

fibres of a specialty yarn as a function of the blending ratio of dyed cotton blended with raw

cotton. He concludes that the average tenacity, elongation and fibre length decreases after pre-

treatment and dyeing. The tenacity of specialty yarns manufactured from dyed and raw cotton

decreased as the percentage of dyed cotton on increased to 40%. The spinnability of these

specialty yarn also decreased as the blending ratio increased.

Change in properties after dyeing: polyester

The concentrations of disperse dyes appear to be one of the major factors for the direction

and extent of the structure transformation in the polyester substrate, with expected influence on

the physical and mechanical properties of the dyed fibres. The different structure sensitive

methods have shown that the lowest concentrations of disperse dyes provoke the further

improvement of the crystal phase in the polyester fibres, followed by the opposite effect from the

relaxation in the medium concentration interval. Most probably the turn in the structural behavior

is caused by the penetration of dye particles in the thicker amorphous areas/inter fibril/ altering

into the composition of the fibre forming polymer.the changes in the supra molecular structure in

the high concentration area are a manifestation of the complex influence of the further

crystallization and the so called by us “cross linking effect”. Because of change in crystal

structure the fibre strength decresed2.

Carding:

The main objectives of carding are;

The process of fibre opening to a state of individual fibres

To remove neps, tiny lumps of fibres and fused fibre ends

To blend fibres

To deliver a continuous sliver for further processing2

Modern pinned licker-in advantages in melange spun yarn

Fibre opening is key to good yarn spinning. Good, gentle opening ensures maximum

retension of fibre strength by minimizing fibre rupture, reducing the level of neps, effective trash

removal and minimal amounts of micro dust and lint. It is obvious that well cleaned and opened

fibre is a prerequisite to high quality carding and spinning. In modern blowrooms, four types of

beaters are primarily used- disc beaters, peg beaters, pinned beaters and saw tooth beater.

Though in modern blowroom lines, it is claimed that less cleaning points are required which

helps reduce fibre damage at high productions rates, what is actually done is that multiple

cleaning points are actually reduced, use of metallic wire leads to aggressive opening and

consequent fibre rupture, which affects ring spun fine yarns quality in particular.

It may be prudent to replace the wire wounds rolls with pinned rolls to reduce fibre

damage. Most super high production lines are suited for open end spinning operations where

quality demands are more forgiving. Machine makes are thus increasingly adopting the pin

technologies to overcome some of the issues posed by aggressive metallic wire cleaning11,12.

Mechanism of fibre breakage

The fibre gets broken in two steps i.e., is every fiber in a tuft has one and only one

opportunity of being caught by a cardwire tooth and having one end freed from the tuft or being

broken at the wire and following the first step, every fiber or fiber segment still partially trapped

within a tuft will be caught a second time by a card wire tooth and will either be freed or broken.

Since we suspected that the maximum load a fiber could sustain without breaking might

depend on the shape of the tooth around which it was looped, we performed simple tensile tests

on wool fibers sampled from a group of sound crossbred staples. Two types of card wire were

used: metallic wire of saw-tooth profile and rectangular cross section, and pointed pins of

circular cross section.

Randomly selected fibers were mounted on cardboard using double-sided adhesive tape,

with a distance of 50 mm between the points of attachment of the fibers. The cardboard mount

was cut into strips so that each strip carried one fiber. A strip was folded and clamped in the

lower jaws of an Instron tensile tester. The cardboard strip was cut carefully so that the fiber

remained intact. A tooth mounted in the upper jaws of the machine was then engaged in the fiber

loop and drawn upwards at 500 mm/minute, the fiber thus being stretched and eventually

breaking13,14

Tooth type No of fibres Breaking load , mN Confidence level

Saw tooth wire 90 513 ±27

Round wire 81 622 ±42

Behavior of fibre in saw tooth and pin type licker-in

Choice of beater and sequence of opening depends on the nature of fibres and the process

requirements. Long staple cotton with low trash would require lesser beating and more opening

than short staple, trashy cotton. Synthetic fibres require no beating and only gentle opening.

Though not preferred, saw tooth wires can be used for opening polyester or nylon fibre.

However, they can cause several problems if used for opening soft fibres like viscose since such

fibres have a tendency to disintegrate under stress.

Opening action of saw tooth wire is characteristically different from pins. The opening

action is done by the knife edges of the saw tooth, which tend to cut open fibres. This causes

fibre rupture and lint generation. This tends to increase the percentage of short fibres and the

level of neps. The trash contained in the fibre supply also tends to disintegrate into micro dust

due to the saw tooth action.

In comparison, the pin has a smooth round surface and a spherical tip, which opens the

fibres through a gentle untangling action. It is obvious that fibre rupture would be minimized as

well as the consequent generation of micro dust and lint would also be reduced considerably with

use of pins. The round profile of pins also has another significant advantage- that of higher

performing life and more consistent quality of opening15.

Advantages of pinned rollers on yarn quality

The improvements are even more dramatic-significant reduction in yarn imperfection,

fibre rupture, fibre loss and trash content in sliver.

In certain cases, more than 50% reduction in imperfections, upto 4% reduction in short

fibre content and more than 2% savings in fibre have been achieved in the card after the

upgrade.

Card production increased 15%.

Successful upgrades have been done on most of the leading makes of high speed cards

and all fibre mixes including short or long staple cotton, viscose, polyester or other

synthetic fibres and for dyed and grey yarn of counts ranging from 2s to 140s12.

Wear and tear of licker-ins

The knife edge gets rounded thus reducing opening action significantly. Moreover, small

cuts or crevices develop on the leading edge of the saw tooth, which tends to ‘catch’ the fibres

and create neps. Usually, the edge of the saw tooth loses its sharpness in the first few months

itself, thus causing a rapid deterioration in the fibre opening action. This is partially mitigated by

grinding the roller so that the teeth regain their sharpness, but this lasts for much less duration

before the deterioration occurs again.

Another significant effect of this loss of sharp edges is that the saw tooth begins to push

fibres rather than open and carry them forward. This obviously results in an increase in fibre

droppage, leading to a loss of rich fiber and lowering of fibre yield.

The pin has a rounded tip; it retains its opening ability much longer. Additionally, the

wear all around the tip causes a new tip to be formed as the old one is eroded, though the pin

length gets slightly reduced. This results in several significant benefits-increases in life of pins,

more consistent opening action, thus ensuring a consistent sliver quality and a higher fibre yield

as compared to saw tooth wires15.

Conclusion

Dyeing of polyester/cotton fibers in their loose state leads to an increased amount of fibre

damage, in comparison to undyed fibres. Instead sliver dyeing is more preferred after carding.

The quality of the melange cotton yarn deteriorates to a considerable extent, as a result, higher

degree of damaged dyed cotton fibres may be mixed with the white ones. So precautions should

be taken in carding process to avoid the damage of dyed fibre. The modern technology like

pinned licker-in intends to avoid excessive such fibre damages. Otherwise spun dyed materials

are preferred rather than synthetic fibres. Because there is no change in fibre properties in the

spun dyed polyester fibres.

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